This invention relates to an insertion tool, and particularly relates to a power driven tool for inserting Tang-free helical coil inserts into tapped openings.
Helical coil inserts have been used for some time to revitalize worn or damaged threads of openings in support structures. Such inserts also have been used to provide a durable threaded opening in support structures which are composed of materials which may not be sufficiently durable to support long-term use of threads therein. The threads of the coil inserts will remain durable for a longer period, compared to the threads of the opening of the support structure, even though there may be frequent removal and reinsertion, or replacement, of threaded fasteners eventually mounted in threaded opening of the coil insert.
The helical coil inserts are typically made from a preformed metal wire, typically formed with a diamond shaped cross-section, which is wound to form a helical coil having successive convolutions. The helical coil is referred to herein as a “coil insert.” The coil insert is wound in such a manner that outer and inner threads are formed by sharp, generally “V” shaped portions on opposite sides of the diamond cross section on the outer and inner surfaces, respectively, of the insert.
The size of the outer threads of the coil insert are consistent with the size of the threads of the opening in the support structure. The size of the inner threads of the coil insert are consistent with the size of the threads typically formed on a portion of the outer surface of the threaded fastener, which is eventually threadedly mounted in coil insert.
In the past, one end of the coil insert was formed with a straight tang to extend diametrically across the immediately adjacent full convolution, and was used to drive the coil insert into the threaded opening of the support structure. In more recent times, the coil insert has not been formed with the tang, but has been formed with a drive notch on the inside of the last convolution near the end of the insert which serves as the facility to drive the insert into the threaded opening of the support structure.
In the past, the coil inserts have been assembled by use of a tool such as, for example, the tool disclosed in U.S. Pat. No. 4,528,737, which issued on Jul. 16, 1985. The tool of the '737 patent includes a rotatable rod having a cutout extending longitudinally through a portion thereof, but which is closed at opposite ends thereof, including a coil insertion end of the tool. The rod is formed with threads on the exterior thereof which begin inboard of the insertion end of the tool and extend toward the opposite end thereof. A longitudinal pawl is mounted pivotally in the cutout and is formed with a pair of lead ramps extending inboard from the insertion end of the pawl. The rod is also formed with a hook portion inboard of the lead ramps and is biased so that the ramps and the hook portion can protrude through a lateral aperture formed through the rod and in communication with the cutout.
In use of the tool of the '737 patent, the coil insert is threadedly assembled on the insertion end of the rod until the biased hook portion is located in the drive notch of the insert. At this juncture, the lead end of the coil insert and the hook portion are located somewhat rearward of the insertion end of the rod and the tool. A power driver is then used to rotate the rod and the pawl, as the insert and rod are inserted into the threaded opening of the support structure, whereby the hook portion drives the insert into the threaded opening.
For at least two reasons the prior art designs (including the '737 design) are less than ideal. First, because the hook of the prior art (e.g., '737) travels in a radially sweeping path toward the coil notch, it changes longitudinal position in the direction of pitch along its path. Because the drive notch of a coil is small, the change in position in the direction of pitch could significantly affect the alignment of the hook with the notch. Second, different amounts of sweep of the hook mean that the hook will have different orientations as it is positioned to engage notches. Therefore, as the hook contacts various coils during installation, such contact will be at different orientations and with different portions of the hook and therefore encourage uneven wear of the hook over time. Such wear may eventually compromises precision engagement between the tool's hook and the drive notch of the coil.
Thus, there is a need for an insertion tool which has a hook portion that extends to engagement with the coil drive notch via a linear motion to minimize the uncertainty of the hook-to-notch path and to maintain perfect alignment of the hook with the drive notch of the coil no matter the size or configuration of the coil. There is also a need to develop a tool that eliminates engagement of the hook with the coil at various orientations of the hook to minimize wear of the hook over time.